The other thing I would add if I was talking to your acquaintance would be to ask if they thought images of naked breasts are always appropriate and inoffensive. And I would give examples of the sort of nakedness that will never appear on page 3 of the Sun.

I think the image this user icon is made from is gorgeous and inspiring; when I brought the poster home my partner said he didn't want it on the wall because he found it disturbing. Which I understood: a lot of people don't want to look at mastectomy scars, even if the woman whose body it is has gotten comfortable with herself. That's a slightly extreme case intended to make the point, but quite a few people complain if they see an old or fat women topless at a beach where nobody is required to wear a shirt.

That of course gets back to the issue of whether women are people in the world, or ornaments for men to enjoy looking at.